Calautti E, Missero C, Stein P L, Ezzell R M, Dotto G P
Cutaneous Biology Research Center, Massachusetts General Hospital, Charlestown 02129, USA.
Genes Dev. 1995 Sep 15;9(18):2279-91. doi: 10.1101/gad.9.18.2279.
Induction of tyrosine phosphorylation is an early and specific event which is required for mouse keratinocyte differentiation to occur, in response to both calcium and TPA (12-0-tetradecanoylphorbol-13-acetate). We report here that there is an increase of tyrosine kinase activity immunoprecipitable with anti-phosphotyrosine antibodies specifically in response to calcium--and a number of other divalent cations--within 2 min of exposure. Such an activity does not correspond to any of the known tyrosine kinases that were tested. A second tyrosine kinase activity is induced in response to both calcium and TPA, and has been identified as fyn, a nonreceptor tyrosine kinase of the src family. fyn activation is induced in keratinocytes within 6 hr of calcium exposure, but already within 2 min of TPA treatment. Cortactin, a p80-85 substrate of src- and fyn-related kinases that localizes with actin at cell adhesion sites, is increasingly tyrosine phosphorylated in calcium- and TPA-induced differentiation, with a time course which parallels that of fyn activation. Keratinocytes with a specific disruption of the fyn, but not yes kinase gene show no induction of phosphorylation of p80-85 proteins, and are significantly altered in their differentiation response both in vitro and in vivo. Thus, at least two tyrosine kinase activities are induced in keratinocyte differentiation, one of which has been identified as fyn and shown to be specifically involved in this process.
酪氨酸磷酸化的诱导是小鼠角质形成细胞分化所必需的早期特异性事件，这一过程是对钙和TPA（12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯）的响应。我们在此报告，在暴露于钙及其他多种二价阳离子后的2分钟内，用抗磷酸酪氨酸抗体免疫沉淀可检测到酪氨酸激酶活性显著增加。这种活性与所测试的任何已知酪氨酸激酶均不对应。第二种酪氨酸激酶活性是对钙和TPA共同响应而诱导产生的，已被鉴定为fyn，它是src家族的一种非受体酪氨酸激酶。在角质形成细胞中，fyn激活在钙暴露6小时内被诱导，但在TPA处理仅2分钟后就已发生。Cortactin是一种与src和fyn相关激酶的p80 - 85底物，定位于细胞黏附位点的肌动蛋白上，在钙和TPA诱导的分化过程中，其酪氨酸磷酸化程度逐渐增加，时间进程与fyn激活平行。fyn基因特异性缺失但yes激酶基因未缺失的角质形成细胞，未显示出p80 - 85蛋白磷酸化的诱导，并且在体外和体内的分化反应均发生了显著改变。因此，在角质形成细胞分化过程中至少诱导了两种酪氨酸激酶活性，其中一种已被鉴定为fyn，并显示其特异性参与了这一过程。
